IFS - FS Helper Functions

Installable File Systems for OS/2
Installable File System Mechanism Installable File System Overview Extended Attributes FSD File Image FSD Initialization IFS Commands File System Function Calls FSD System Interfaces FSD Calling Conventions and Requirements FS Service Routines FS Helper Functions Remote IPL / Bootable IFS mini-FDS Entry Points mini-FDS Helper Routines

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The following table summarizes the routines that make up the File System Helper interface between FSDs and the kernel.

FS Helper Routine    Description
────────────────────────────────────────────────────────
FSH_ADDSHARE         Add a name to the sharing set
────────────────────────────────────────────────────────
FSH_BUFSTATE         REMOVED in OS/2 Version 2.0
────────────────────────────────────────────────────────
FSH_CALLDRIVER       Call Device Driver's Extended
                     Strategy entry point
────────────────────────────────────────────────────────
FSH_CANONICALIZE     Convert pathname to canonical form
────────────────────────────────────────────────────────
FSH_CHECKEANAME      Check EA name validity
────────────────────────────────────────────────────────
FSH_CRITERROR        Signal a hard error to the daemon
────────────────────────────────────────────────────────
FSH_DEVIOCTL         Send IOCTL request to device driver
────────────────────────────────────────────────────────
FSH_DOVOLIO          Volume-based sector-oriented
                     transfer
────────────────────────────────────────────────────────
FSH_DOVOLIO2         Send volume-based IOCTL request to
                     device driver.
────────────────────────────────────────────────────────
FSH_FINDCHAR         Find first occurrence of char in
                     string
────────────────────────────────────────────────────────
FSH_FINDDUPHVPB      Locates equivalent hVPBs
────────────────────────────────────────────────────────
FSH_FLUSHBUF         REMOVED in OS/2 Version 2.0
────────────────────────────────────────────────────────
FSH_FORCENOSWAP      Force segments permanently into
                     memory
────────────────────────────────────────────────────────
FSH_GETBUF           REMOVED in OS/2 Version 2.0
────────────────────────────────────────────────────────
FSH_GETFIRSTOVERLAPB REMOVED in OS/2 Version 2.0
────────────────────────────────────────────────────────
FSH_GETPRIORITY      Get current thread's I/O priority
────────────────────────────────────────────────────────
FSH_GETVOLPARM       Get VPB data from VPB handle
────────────────────────────────────────────────────────
FSH_INTERR           Signal an internal error
────────────────────────────────────────────────────────
FSH_IOBOOST          Gives the current thread an I/O
                     priority boost
────────────────────────────────────────────────────────
FSH_IOSEMCLEAR       Clear an I/O-event semaphore
────────────────────────────────────────────────────────
FSH_ISCURDIRPREFIX   Test for a prefix of a current
                     directory
────────────────────────────────────────────────────────
FSH_LOADCHAR         Load character from a string
────────────────────────────────────────────────────────
FSH_NAMEFROMSFN      Get the full path name from an SFN
────────────────────────────────────────────────────────
FSH_PREVCHAR         Move backward in string
────────────────────────────────────────────────────────
FSH_PROBEBUF         User address validity check
────────────────────────────────────────────────────────
FSH_QSYSINFO         Query system information
────────────────────────────────────────────────────────
FSH_REGISTERPERFCTRS Register a FSD with PERFVIEW
────────────────────────────────────────────────────────
FSH_RELEASEBUF       REMOVED in OS/2 Version 2.0
────────────────────────────────────────────────────────
FSH_REMOVESHARE      Remove a name from the sharing set
────────────────────────────────────────────────────────
FSH_SEGALLOC         Allocate a GDT or LDT segment
────────────────────────────────────────────────────────
FSH_SEGFREE          Release a GDT or LDT segment
────────────────────────────────────────────────────────
FSH_SEGREALLOC       Change segment size
────────────────────────────────────────────────────────
FSH_SEMCLEAR         Clear a semaphore
────────────────────────────────────────────────────────
FSH_SEMREQUEST       Request a semaphore
────────────────────────────────────────────────────────
FSH_SEMSET           Set a semaphore
────────────────────────────────────────────────────────
FSH_SEMSETWAIT       Set a semaphore and wait for clear
────────────────────────────────────────────────────────
FSH_SEMWAIT          Wait for clear
────────────────────────────────────────────────────────
FSH_SETVOLUME        force a volume to be mounted on the
                     drive
────────────────────────────────────────────────────────
FSH_STORECHAR        Store character into string
────────────────────────────────────────────────────────
FSH_UPPERCASE        Uppercase ASCIIZ string
────────────────────────────────────────────────────────
FSH_WILDMATCH        Match using OS/2 wildcards
────────────────────────────────────────────────────────
FSH_YIELD            Yield CPU to higher priority
                     threads

FSDs are loaded as dynamic link libraries and may import services provided by the kernel. These services can be called directly by the file system, passing the relevant parameters.

No validation of input parameters is done unless otherwise specified. The FSD calls FSH_PROBEBUF, where appropriate, before calling the FS help routine.

When any service returns an error code, the FSD must return to the caller as soon as possible and return the specific error code from the helper to the FS router .

There are many deadlocks that may occur as a result of operations issued by FSDs. OS/2 provides no means whereby deadlocks between file systems and applications can be detected.